We propose to further determine the functional and connectional organization of the dorsal stream visuomotor pathway from visual areas to motor areas. (1) We will identify functional subregions of posterior parietal cortex using microelectrode stimulation and optical imaging of evoked cortical activity. (2) Tracers will be injected in identified subregions and areas of cortex to reveal the cortical and subcortical connectional network. (3) We will evaluate the functional plasticity of posterior parietal subregions as a result of training on visuomotor tasks. (4) Finally, the functional contributions of subdivisions of the dorsal stream system to the performance of visuomotor tasks and the plasticity of the system will be evaluated after lesions of dorsal stream visual areas and parts of posterior parietal cortex. The results of these experiments will provide a new and extended understanding of the functional organization of the subsystem for visuomotor behavior in primates. In addition, the results will inform clinical interpretations of the consequences of damage to the visuomotor system in humans, and suggest mechanisms of recovery. Favorable therapeutic procedures may be based on the results. PUBLIC HEALTH RELEVANCE: The proposed research will help determine how posterior parietal cortex links vision to action. The studies will define functional subdivisions of posterior parietal cortex, determine how these subdivisions fit into a connectional network, and evaluate the behavioral consequences of the loss of visual inputs to the network.